This disclosure relates to compositions having reduced frictional coefficients, methods of manufacture thereof and to articles comprising the same.
Organic polymers such as polyamides, polyesters, polycarbonates, and the like, are engineering thermoplastics and are frequently used in a variety of applications ranging from gears, cams, rollers, bearings, nuts and bolts, power tool housings, electrical connectors, combs, coil formers, fuel tanks for cars and kitchen utensils amongst other things. These engineering polymers frequently contact a metal counterface (i.e., a metal counterface that is opposed to a face of the engineering polymer) and over long periods of time under various conditions of mechanical stress, the surface of the polymer tends to develop wear cracks because of friction between the polymer and the metal counterface.
Several lubricants are used to counter this problem ranging from base oils (liquid lubricants) to a variety of solid lubricants including boron nitride, polytetrafluoroethylene (PTFE), graphite, and molybdenum disulfide. Many of these lubricants form a boundary film between the polymer surface and the metal counterface. However, frictional heat generated at the boundary causes degradation and evaporation of the lubricants.
For example, polyolefins and fluorinated ethylenes (e.g., polytetrafluoroethylene (PTFE)) are often used as lubricants in amounts of about 20 wt % in a polyamide (nylon 6) in order to improve the wear and frictional properties of the polyamide. The polytetrafluoroethylene forms a film between the polyamide and the metal counterface, thus reducing the coefficient of friction and thus the wear. The large amounts of polytetrafluoroethylene however, make the resulting polyamide very expensive. In addition, at very high temperatures the polytetrafluoroethylene also degrades to form volatile components that are environmentally hazardous.
It is therefore desirable to develop organic polymers and organic polymeric compositions that have low coefficients of friction that are inexpensive and that can use smaller amounts of an additive to reduce the coefficient of friction.